"Too many workplaces lack clear policies about how to handle accusations of sexual harassment," Sandberg wrote in a post on Facebook.

Facebook COO Sheryl Sandberg is speaking up about her experiences with sexual harassment as part of a call for "systemic" changes in the workplace.

The author of Lean In wrote in a post on Facebook that while she's never been sexually harassed or assaulted by someone she has worked for, she has experienced unwanted sexual advances in workplace settings over the years. The instances she described include "A hand on my leg under the table at a meeting. Married men — all decades older than I — offering 'career advice' and then suggesting that they could share it with me alone late at night. The conference where a man I declined leaving a dinner with came to my hotel room late at night and banged on my door until I called security."

She wrote that such interactions have occurred less as she has become more powerful in her career, but that they do still happen. The conclusion Sandberg drew from these experiences was that these men "feel that they have more power than I do."

Sandberg said that "we need systemic, lasting changes that deter bad behavior and protect everyone, from professionals climbing the corporate ladder to workers in low-paid positions who often have little power." She also called out many workplaces for not having clear policies for handling sexual harassment allegations. Her recommendation for correcting that is to develop "clear principles, then institute policies to support them."

Sandberg has been in a senior leadership position at Facebook since 2008, when she became the first woman to hold a board seat with the social network. She has been vocal about the work that needs to be done to bring more women into leadership positions, including at Facebook where women hold 35 percent of all roles and 28 percent of senior leadership roles.

CEO Mark Zuckerberg responded to Sandberg's note thanking her for her leadership. "This is so important and I know the advice to establish clear principles and policies will help improve many organizations," he wrote.

She shared her thoughts as Hollywood and Silicon Valley both grapple with how to enact change following a wave of sexual harassment allegations against well-known and powerful men, from Harvey Weinstein to investor Shervin Pishevar.

Sandberg ended her post by noting that one way to create change would be to encourage more women to take positions of power. "It wouldn't solve all the problems we face if more women were in power — although I believe we could get quite a lot of good done," she wrote. "But one thing's for certain: many fewer people would be groped and worse while trying to do their jobs. And that would be a major step in the right direction."